1. Field of the Invention
The invention relates to an optical element, and more particularly to an optical element achieving the requirements of light polarization, light integration, and brightness uniformity.
2. Description of the Related Art
Due to the advantages of compactness, light weight, and low power consumption, liquid crystal displays (LCD) have become widely used in electronic product applications, such as monitors, notebook computers, digital cameras, projectors, and mobile phones.
A backlight module is one of the key components of an LCD. Since the LCD panel does not generate light itself, the backlight module is responsible for providing sufficient light and uniform luminance for the LCD panel. Presently, LCDs are broadly used in several electronic products, such as monitors, notebooks, and large-size LCD-TVs. Consequently, the demand for backlight units and related components is growing.
FIG. 1 is a cross-section view of a conventional backlight module 10 including a light source 12, reflector 14, diffusion plate 16, diffusion sheet 18, and a prism sheet 20, assembled and joined together. As illustrated, it is difficult to further improve the brightness, light weight, and thin characteristics of the conventional backlight module 10.
Thus, a backlight module with a combined diffusion plate and brightness enhancement film has been developed. The backlight module enhances the brightness by integrated optical and polarized light effect. However, the brightness enhancement film increases costs and complicates fabrication of the LCD.
As such, U.S. Pat. No. 7,220,036 discloses a liquid crystal display 100 including a liquid crystal display panel 102 and a backlight module 110, as shown in FIG. 2. The liquid crystal display panel 102 includes a top substrate 104, a bottom substrate 106, and a liquid crystal layer 108, and the backlight module 110 includes a brightness enhancement film 114 on a prism sheet 112, a bottom diffusion sheet 116, diffusion plate 118, reflector 120 and a light source 122. Thus, illumination of the liquid crystal display 100 is enhanced, diffused, and integrated. However, since the backlight module 110 is assembled from a plurality of laminations, fabrication of the LCD is complicated and yield of the backlight module 110 is decreased. Further, disadvantages concerning transfer problems, superimposed traces, and structural damage caused during assembly significantly limit practical applications of the backlight module 110 in the LCD industry. Specifically, the brightness enhancement film 114 is a complex film made by coextrusion of a multitude (one thousand or more) of alternating polymer layers with distinct reflective indexes in an optical axis. Moreover, due to optical characteristics of the LCD, the backlight module 110 is combined with the prism sheet and the bottom diffusion sheet, thus increasing weight and thickness of the backlight module 110, which is contrary to present trends.
Therefore, a novel, light, thin, low powered, and bright backlight module, fabricated at low cost and applicable to large-sized application is desirable.